/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.andengine.util.base64;

import java.io.UnsupportedEncodingException;

import android.util.Base64OutputStream;

/**
 * Utilities for encoding and decoding the Base64 representation of
 * binary data.  See RFCs <a
 * href="http://www.ietf.org/rfc/rfc2045.txt">2045</a> and <a
 * href="http://www.ietf.org/rfc/rfc3548.txt">3548</a>.
 */
public class Base64 {
	/**
	 * Default values for encoder/decoder flags.
	 */
	public static final int DEFAULT = 0;

	/**
	 * Encoder flag bit to omit the padding '=' characters at the end
	 * of the output (if any).
	 */
	public static final int NO_PADDING = 1;

	/**
	 * Encoder flag bit to omit all line terminators (i.e., the output
	 * will be on one long line).
	 */
	public static final int NO_WRAP = 2;

	/**
	 * Encoder flag bit to indicate lines should be terminated with a
	 * CRLF pair instead of just an LF.  Has no effect if {@code
	 * NO_WRAP} is specified as well.
	 */
	public static final int CRLF = 4;

	/**
	 * Encoder/decoder flag bit to indicate using the "URL and
	 * filename safe" variant of Base64 (see RFC 3548 section 4) where
	 * {@code -} and {@code _} are used in place of {@code +} and
	 * {@code /}.
	 */
	public static final int URL_SAFE = 8;

	/**
	 * Flag to pass to {@link Base64OutputStream} to indicate that it
	 * should not close the output stream it is wrapping when it
	 * itself is closed.
	 */
	public static final int NO_CLOSE = 16;

	//  --------------------------------------------------------
	//  shared code
	//  --------------------------------------------------------

	/* package */ static abstract class Coder {
		public byte[] output;
		public int op;

		/**
		 * Encode/decode another block of input data.  this.output is
		 * provided by the caller, and must be big enough to hold all
		 * the coded data.  On exit, this.opwill be set to the length
		 * of the coded data.
		 *
		 * @param finish true if this is the final call to process for
		 *        this object.  Will finalize the coder state and
		 *        include any final bytes in the output.
		 *
		 * @return true if the input so far is good; false if some
		 *         error has been detected in the input stream..
		 */
		public abstract boolean process(byte[] input, int offset, int len, boolean finish);

		/**
		 * @return the maximum number of bytes a call to process()
		 * could produce for the given number of input bytes.  This may
		 * be an overestimate.
		 */
		public abstract int maxOutputSize(int len);
	}

	//  --------------------------------------------------------
	//  decoding
	//  --------------------------------------------------------

	/**
	 * Decode the Base64-encoded data in input and return the data in
	 * a new byte array.
	 *
	 * <p>The padding '=' characters at the end are considered optional, but
	 * if any are present, there must be the correct number of them.
	 *
	 * @param str    the input String to decode, which is converted to
	 *               bytes using the default charset
	 * @param flags  controls certain features of the decoded output.
	 *               Pass {@code DEFAULT} to decode standard Base64.
	 *
	 * @throws IllegalArgumentException if the input contains
	 * incorrect padding
	 */
	public static byte[] decode(final String str, final int flags) {
		return Base64.decode(str.getBytes(), flags);
	}

	/**
	 * Decode the Base64-encoded data in input and return the data in
	 * a new byte array.
	 *
	 * <p>The padding '=' characters at the end are considered optional, but
	 * if any are present, there must be the correct number of them.
	 *
	 * @param input the input array to decode
	 * @param flags  controls certain features of the decoded output.
	 *               Pass {@code DEFAULT} to decode standard Base64.
	 *
	 * @throws IllegalArgumentException if the input contains
	 * incorrect padding
	 */
	public static byte[] decode(final byte[] input, final int flags) {
		return Base64.decode(input, 0, input.length, flags);
	}

	/**
	 * Decode the Base64-encoded data in input and return the data in
	 * a new byte array.
	 *
	 * <p>The padding '=' characters at the end are considered optional, but
	 * if any are present, there must be the correct number of them.
	 *
	 * @param input  the data to decode
	 * @param offset the position within the input array at which to start
	 * @param len    the number of bytes of input to decode
	 * @param flags  controls certain features of the decoded output.
	 *               Pass {@code DEFAULT} to decode standard Base64.
	 *
	 * @throws IllegalArgumentException if the input contains
	 * incorrect padding
	 */
	public static byte[] decode(final byte[] input, final int offset, final int len, final int flags) {
		// Allocate space for the most data the input could represent.
		// (It could contain less if it contains whitespace, etc.)
		final Decoder decoder = new Decoder(flags, new byte[len*3/4]);

		if (!decoder.process(input, offset, len, true)) {
			throw new IllegalArgumentException("bad base-64");
		}

		// Maybe we got lucky and allocated exactly enough output space.
		if (decoder.op == decoder.output.length) {
			return decoder.output;
		}

		// Need to shorten the array, so allocate a new one of the
		// right size and copy.
		final byte[] temp = new byte[decoder.op];
		System.arraycopy(decoder.output, 0, temp, 0, decoder.op);
		return temp;
	}

	/* package */ static class Decoder extends Coder {
		/**
		 * Lookup table for turning bytes into their position in the
		 * Base64 alphabet.
		 */
		private static final int DECODE[] = {
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
			52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
			-1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
			15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
			-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
			41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		};

		/**
		 * Decode lookup table for the "web safe" variant (RFC 3548
		 * sec. 4) where - and _ replace + and /.
		 */
		private static final int DECODE_WEBSAFE[] = {
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1,
			52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
			-1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
			15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63,
			-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
			41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		};

		/** Non-data values in the DECODE arrays. */
		private static final int SKIP = -1;
		private static final int EQUALS = -2;

		/**
		 * States 0-3 are reading through the next input tuple.
		 * State 4 is having read one '=' and expecting exactly
		 * one more.
		 * State 5 is expecting no more data or padding characters
		 * in the input.
		 * State 6 is the error state; an error has been detected
		 * in the input and no future input can "fix" it.
		 */
		private int state;   // state number (0 to 6)
		private int value;

		final private int[] alphabet;

		public Decoder(final int flags, final byte[] output) {
			this.output = output;

			this.alphabet = ((flags & URL_SAFE) == 0) ? DECODE : DECODE_WEBSAFE;
			this.state = 0;
			this.value = 0;
		}

		/**
		 * @return an overestimate for the number of bytes {@code
		 * len} bytes could decode to.
		 */
		@Override
		public int maxOutputSize(final int len) {
			return len * 3/4 + 10;
		}

		/**
		 * Decode another block of input data.
		 *
		 * @return true if the state machine is still healthy.  false if
		 *         bad base-64 data has been detected in the input stream.
		 */
		@Override
		public boolean process(final byte[] input, final int offset, int len, final boolean finish) {
			if (this.state == 6) {
				return false;
			}

			int p = offset;
			len += offset;

			// Using local variables makes the decoder about 12%
			// faster than if we manipulate the member variables in
			// the loop.  (Even alphabet makes a measurable
			// difference, which is somewhat surprising to me since
			// the member variable is final.)
			int state = this.state;
			int value = this.value;
			int op = 0;
			final byte[] output = this.output;
			final int[] alphabet = this.alphabet;

			while (p < len) {
				// Try the fast path:  we're starting a new tuple and the
				// next four bytes of the input stream are all data
				// bytes.  This corresponds to going through states
				// 0-1-2-3-0.  We expect to use this method for most of
				// the data.
				//
				// If any of the next four bytes of input are non-data
				// (whitespace, etc.), value will end up negative.  (All
				// the non-data values in decode are small negative
				// numbers, so shifting any of them up and or'ing them
				// together will result in a value with its top bit set.)
				//
				// You can remove this whole block and the output should
				// be the same, just slower.
				if (state == 0) {
					while (p+4 <= len &&
							(value = ((alphabet[input[p] & 0xff] << 18) |
									(alphabet[input[p+1] & 0xff] << 12) |
									(alphabet[input[p+2] & 0xff] << 6) |
									(alphabet[input[p+3] & 0xff]))) >= 0) {
						output[op+2] = (byte) value;
						output[op+1] = (byte) (value >> 8);
						output[op] = (byte) (value >> 16);
						op += 3;
						p += 4;
					}
					if (p >= len) {
						break;
					}
				}

				// The fast path isn't available -- either we've read a
				// partial tuple, or the next four input bytes aren't all
				// data, or whatever.  Fall back to the slower state
				// machine implementation.

				final int d = alphabet[input[p++] & 0xff];

				switch (state) {
					case 0:
						if (d >= 0) {
							value = d;
							++state;
						} else if (d != SKIP) {
							this.state = 6;
							return false;
						}
						break;

					case 1:
						if (d >= 0) {
							value = (value << 6) | d;
							++state;
						} else if (d != SKIP) {
							this.state = 6;
							return false;
						}
						break;

					case 2:
						if (d >= 0) {
							value = (value << 6) | d;
							++state;
						} else if (d == EQUALS) {
							// Emit the last (partial) output tuple;
							// expect exactly one more padding character.
							output[op++] = (byte) (value >> 4);
							state = 4;
						} else if (d != SKIP) {
							this.state = 6;
							return false;
						}
						break;

					case 3:
						if (d >= 0) {
							// Emit the output triple and return to state 0.
							value = (value << 6) | d;
							output[op+2] = (byte) value;
							output[op+1] = (byte) (value >> 8);
							output[op] = (byte) (value >> 16);
							op += 3;
							state = 0;
						} else if (d == EQUALS) {
							// Emit the last (partial) output tuple;
							// expect no further data or padding characters.
							output[op+1] = (byte) (value >> 2);
							output[op] = (byte) (value >> 10);
							op += 2;
							state = 5;
						} else if (d != SKIP) {
							this.state = 6;
							return false;
						}
						break;

					case 4:
						if (d == EQUALS) {
							++state;
						} else if (d != SKIP) {
							this.state = 6;
							return false;
						}
						break;

					case 5:
						if (d != SKIP) {
							this.state = 6;
							return false;
						}
						break;
				}
			}

			if (!finish) {
				// We're out of input, but a future call could provide
				// more.
				this.state = state;
				this.value = value;
				this.op = op;
				return true;
			}

			// Done reading input.  Now figure out where we are left in
			// the state machine and finish up.

			switch (state) {
				case 0:
					// Output length is a multiple of three.  Fine.
					break;
				case 1:
					// Read one extra input byte, which isn't enough to
					// make another output byte.  Illegal.
					this.state = 6;
					return false;
				case 2:
					// Read two extra input bytes, enough to emit 1 more
					// output byte.  Fine.
					output[op++] = (byte) (value >> 4);
					break;
				case 3:
					// Read three extra input bytes, enough to emit 2 more
					// output bytes.  Fine.
					output[op++] = (byte) (value >> 10);
					output[op++] = (byte) (value >> 2);
					break;
				case 4:
					// Read one padding '=' when we expected 2.  Illegal.
					this.state = 6;
					return false;
				case 5:
					// Read all the padding '='s we expected and no more.
					// Fine.
					break;
			}

			this.state = state;
			this.op = op;
			return true;
		}
	}

	//  --------------------------------------------------------
	//  encoding
	//  --------------------------------------------------------

	/**
	 * Base64-encode the given data and return a newly allocated
	 * String with the result.
	 *
	 * @param input  the data to encode
	 * @param flags  controls certain features of the encoded output.
	 *               Passing {@code DEFAULT} results in output that
	 *               adheres to RFC 2045.
	 */
	public static String encodeToString(final byte[] input, final int flags) {
		try {
			return new String(Base64.encode(input, flags), "US-ASCII");
		} catch (final UnsupportedEncodingException e) {
			// US-ASCII is guaranteed to be available.
			throw new AssertionError(e);
		}
	}

	/**
	 * Base64-encode the given data and return a newly allocated
	 * String with the result.
	 *
	 * @param input  the data to encode
	 * @param offset the position within the input array at which to
	 *               start
	 * @param len    the number of bytes of input to encode
	 * @param flags  controls certain features of the encoded output.
	 *               Passing {@code DEFAULT} results in output that
	 *               adheres to RFC 2045.
	 */
	public static String encodeToString(final byte[] input, final int offset, final int len, final int flags) {
		try {
			return new String(Base64.encode(input, offset, len, flags), "US-ASCII");
		} catch (final UnsupportedEncodingException e) {
			// US-ASCII is guaranteed to be available.
			throw new AssertionError(e);
		}
	}

	/**
	 * Base64-encode the given data and return a newly allocated
	 * byte[] with the result.
	 *
	 * @param input  the data to encode
	 * @param flags  controls certain features of the encoded output.
	 *               Passing {@code DEFAULT} results in output that
	 *               adheres to RFC 2045.
	 */
	public static byte[] encode(final byte[] input, final int flags) {
		return Base64.encode(input, 0, input.length, flags);
	}

	/**
	 * Base64-encode the given data and return a newly allocated
	 * byte[] with the result.
	 *
	 * @param input  the data to encode
	 * @param offset the position within the input array at which to
	 *               start
	 * @param len    the number of bytes of input to encode
	 * @param flags  controls certain features of the encoded output.
	 *               Passing {@code DEFAULT} results in output that
	 *               adheres to RFC 2045.
	 */
	public static byte[] encode(final byte[] input, final int offset, final int len, final int flags) {
		final Encoder encoder = new Encoder(flags, null);

		// Compute the exact length of the array we will produce.
		int output_len = len / 3 * 4;

		// Account for the tail of the data and the padding bytes, if any.
		if (encoder.do_padding) {
			if (len % 3 > 0) {
				output_len += 4;
			}
		} else {
			switch (len % 3) {
				case 0: break;
				case 1: output_len += 2; break;
				case 2: output_len += 3; break;
			}
		}

		// Account for the newlines, if any.
		if (encoder.do_newline && len > 0) {
			output_len += (((len-1) / (3 * Encoder.LINE_GROUPS)) + 1) *
			(encoder.do_cr ? 2 : 1);
		}

		encoder.output = new byte[output_len];
		encoder.process(input, offset, len, true);

		assert encoder.op == output_len;

		return encoder.output;
	}

	/* package */ static class Encoder extends Coder {
		/**
		 * Emit a new line every this many output tuples.  Corresponds to
		 * a 76-character line length (the maximum allowable according to
		 * <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>).
		 */
		public static final int LINE_GROUPS = 19;

		/**
		 * Lookup table for turning Base64 alphabet positions (6 bits)
		 * into output bytes.
		 */
		private static final byte ENCODE[] = {
			'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
			'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
			'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
			'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/',
		};

		/**
		 * Lookup table for turning Base64 alphabet positions (6 bits)
		 * into output bytes.
		 */
		private static final byte ENCODE_WEBSAFE[] = {
			'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
			'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
			'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
			'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '_',
		};

		final private byte[] tail;
		/* package */ int tailLen;
		private int count;

		final public boolean do_padding;
		final public boolean do_newline;
		final public boolean do_cr;
		final private byte[] alphabet;

		public Encoder(final int flags, final byte[] output) {
			this.output = output;

			this.do_padding = (flags & NO_PADDING) == 0;
			this.do_newline = (flags & NO_WRAP) == 0;
			this.do_cr = (flags & CRLF) != 0;
			this.alphabet = ((flags & URL_SAFE) == 0) ? ENCODE : ENCODE_WEBSAFE;

			this.tail = new byte[2];
			this.tailLen = 0;

			this.count = this.do_newline ? LINE_GROUPS : -1;
		}

		/**
		 * @return an overestimate for the number of bytes {@code
		 * len} bytes could encode to.
		 */
		@Override
		public int maxOutputSize(final int len) {
			return len * 8/5 + 10;
		}

		@Override
		public boolean process(final byte[] input, final int offset, int len, final boolean finish) {
			// Using local variables makes the encoder about 9% faster.
			final byte[] alphabet = this.alphabet;
			final byte[] output = this.output;
			int op = 0;
			int count = this.count;

			int p = offset;
			len += offset;
			int v = -1;

			// First we need to concatenate the tail of the previous call
			// with any input bytes available now and see if we can empty
			// the tail.

			switch (this.tailLen) {
				case 0:
					// There was no tail.
					break;

				case 1:
					if (p+2 <= len) {
						// A 1-byte tail with at least 2 bytes of
						// input available now.
						v = ((this.tail[0] & 0xff) << 16) |
						((input[p++] & 0xff) << 8) |
						(input[p++] & 0xff);
						this.tailLen = 0;
					}
					break;

				case 2:
					if (p+1 <= len) {
						// A 2-byte tail with at least 1 byte of input.
						v = ((this.tail[0] & 0xff) << 16) |
						((this.tail[1] & 0xff) << 8) |
						(input[p++] & 0xff);
						this.tailLen = 0;
					}
					break;
			}

			if (v != -1) {
				output[op++] = alphabet[(v >> 18) & 0x3f];
				output[op++] = alphabet[(v >> 12) & 0x3f];
				output[op++] = alphabet[(v >> 6) & 0x3f];
				output[op++] = alphabet[v & 0x3f];
				if (--count == 0) {
					if (this.do_cr) {
						output[op++] = '\r';
					}
					output[op++] = '\n';
					count = LINE_GROUPS;
				}
			}

			// At this point either there is no tail, or there are fewer
			// than 3 bytes of input available.

			// The main loop, turning 3 input bytes into 4 output bytes on
			// each iteration.
			while (p+3 <= len) {
				v = ((input[p] & 0xff) << 16) |
				((input[p+1] & 0xff) << 8) |
				(input[p+2] & 0xff);
				output[op] = alphabet[(v >> 18) & 0x3f];
				output[op+1] = alphabet[(v >> 12) & 0x3f];
				output[op+2] = alphabet[(v >> 6) & 0x3f];
				output[op+3] = alphabet[v & 0x3f];
				p += 3;
				op += 4;
				if (--count == 0) {
					if (this.do_cr) {
						output[op++] = '\r';
					}
					output[op++] = '\n';
					count = LINE_GROUPS;
				}
			}

			if (finish) {
				// Finish up the tail of the input.  Note that we need to
				// consume any bytes in tail before any bytes
				// remaining in input; there should be at most two bytes
				// total.

				if (p-this.tailLen == len-1) {
					int t = 0;
					v = ((this.tailLen > 0 ? this.tail[t++] : input[p++]) & 0xff) << 4;
					this.tailLen -= t;
					output[op++] = alphabet[(v >> 6) & 0x3f];
					output[op++] = alphabet[v & 0x3f];
					if (this.do_padding) {
						output[op++] = '=';
						output[op++] = '=';
					}
					if (this.do_newline) {
						if (this.do_cr) {
							output[op++] = '\r';
						}
						output[op++] = '\n';
					}
				} else if (p-this.tailLen == len-2) {
					int t = 0;
					v = (((this.tailLen > 1 ? this.tail[t++] : input[p++]) & 0xff) << 10) |
					(((this.tailLen > 0 ? this.tail[t++] : input[p++]) & 0xff) << 2);
					this.tailLen -= t;
					output[op++] = alphabet[(v >> 12) & 0x3f];
					output[op++] = alphabet[(v >> 6) & 0x3f];
					output[op++] = alphabet[v & 0x3f];
					if (this.do_padding) {
						output[op++] = '=';
					}
					if (this.do_newline) {
						if (this.do_cr) {
							output[op++] = '\r';
						}
						output[op++] = '\n';
					}
				} else if (this.do_newline && op > 0 && count != LINE_GROUPS) {
					if (this.do_cr) {
						output[op++] = '\r';
					}
					output[op++] = '\n';
				}

				assert this.tailLen == 0;
				assert p == len;
			} else {
				// Save the leftovers in tail to be consumed on the next
				// call to encodeInternal.

				if (p == len-1) {
					this.tail[this.tailLen++] = input[p];
				} else if (p == len-2) {
					this.tail[this.tailLen++] = input[p];
					this.tail[this.tailLen++] = input[p+1];
				}
			}

			this.op = op;
			this.count = count;

			return true;
		}
	}

	private Base64() { }   // don't instantiate
}
